The invention relates to a water changing device in a seedling growing and culturing pond for marine products. The water changing device comprises a framework, wherein the periphery and the bottom ofthe framework are covered by purse seines; floating balls are arranged at the top of the framework; buoyancy generated by the floating balls in water is greater than the weight of the framework; a water feeding and draining device is arranged inside the framework; an inner cavity of the water feeding and draining device is communicated with the inner part of the framework; a water body inside theframework can freely enter the inner cavity of the water feeding and draining device; at least one water through hole is formed in the water feeding and draining device; a water pipe is connected to each water through hole. The water changing device disclosed by the invention has the advantages that the structure is reasonable, water change efficiency can be greatly improved and disturbance to sediments at the bottom of the pond is reduced; by changing an operation mode, the water changing device can be used for cleaning the sediments at the bottom of the pond, and further the aim of multiplefunctions by one object is achieved.